Guide roll construction and utilization

ABSTRACT

A ROLL USED FOR GUIDING METAL STRIP OR SHEET MATERIAL THROUGH A FURNACE OF HOLLOW CONSTRUCTION IS PROVIDED WITH PERFORATIONS OR OPENINGS IN ITS GUIDE SURFACE FOR SUPPLYING AN INERT GAS, SUCH AS NITROGEN, TO LUBRICATE THE ROLL AND   PROVIDE AN ADHERING FILM OF THE GAS ON THE COOPERTAING SURFACE OF THE METAL MATERIAL.

March 14, J. T MAYHEW GUIDE ROLL CONSTRUCTION AND UTILIZATION Filed Jan. 15, 1970 INVENTOR.

JOHN T. MAY H EW H/S A TTOPNE VS United States Pater 3,649,381 GUIDE ROLL CONSTRUCTION AND UTILIZATION John T. Mayhew, 156 Sunset Drive, Toronto, Ohio 43964 Filed Jan. 15, 1970, Ser. No. 3,072 Int. Cl. C21d 9/56 U.S. Cl. 148-156 5 Claims ABSTRACT OF THE DISCLOSURE A roll used for guiding metal strip or sheet material through a furnace of hollow construction is provided with perforations or openings in its guide surface for supplying an inert gas, such as nitrogen, to lubricate the roll and provide an adhering film of the gas on the cooperating surface of the metal material.

This invention relates to an improved guide roll construction and utilization as used under elevated temperature conditions, such as in an annealing or heat treating furnace. A phase of the invention deals with the elimination of metal pick-up by a guide roller from a moving metal member or workpiece, particularly where the member is being advanced along a furnace chamber on a guide roll positioned in the furnace.

There has heretofore been a serious problem from the standpoint of so-called metal pick-up on rolls, such as used in guiding metal strip and the like through a furnace. The problem has arisen due to the impossibility or impracticability of fully synchronizing the speed of all of the rolls with the rate of movement of the metal strip or sheet. That is, some of the carrying or guide rolls tend to move or rotate slower or faster than others and even where the strip and an associated roll are in synchronism, there may be some slippage therebetween, with the result that the inner side of the strip is rubbed which produces what may be termed a chemical reaction that deposits a slight amount of steel or metal of the strip on the surface of the roll. When this occurs, atoms of chromium, nickel or other alloying elements (depending upon the alloying content of the rolls) tend to migrate into, for example, steel de posited on the roll from the strip. The deposit builds-up and becomes larger in diameter and thus tends to take-up more steel from the strip as the operation progresses. As the build-up becomes thicker, the damage to the surface of the strip becomes greater. Unfortunately this build-up increases rapidly once it is initiated and, in addition to its tendency to form scratches and dinges on the strip or workpiece, tends to release chunks of the material that welds to the bottom of the strip. This, of course, causes serious difiiculty, particularly if, for example, a steel strip is being recoiled. It is apparent that defects thus produced result in the rejection of steel for various purposes, such as used for an automobile body.

This difiiculty occurs whether or not a strip is being moved entirely by tension through the furnace with the guide rolls being non-driven as idler rolls, or where the rolls or some of them are driven to at least aid in the through-put movement of the strip, sheet or workpiece. In a furnace having a typical temperature in the neighborhood of 1700 to 1800 F., the above type of pick-up or build-up appears to be accelerated and coated rolls have a tendency to stick to, tear or damage the surface of the strip which it is desired to provide with as high a finish as possible. Of course, the rolls must be rotated to prevent their warpage and to minimize the frictional engagement between them and the strip. An appreciable build-up such as produced in the manner above outlined will also tend to damage a strip leveler.

In view of the above, it has been an object of the invention to eliminate the above difiiculties which require frequent replacement of the rolls and frequent rejection of steel strip and sheet material, and to do so without the necessity of endeavoring to fully synchronize all of the furnace rolls with the speed of movement of the strip.

Another object of the invention has been to develop a new approach to the problem here presented which will be fully effective in eliminating the adverse action and the attendant adverse results.

A further object of the invention has been to provide a simple and practical as well as an efficient method and means of preventing the build-up of metal from a strip or sheet being guided on the surface of a guide roll through or in a furnace chamber.

A still further object of the invention has been to provide insulating and protective means between a strip and a cooperating guide roll which will eliminate the adverse conditions, and which will tend to adhere and move along the guided surface of the metal sheet or strip.

These and other objects of the invention will appear to those skilled in the art from the illustrated embodiment, the drawings and the claims.

FIG. 1 is a somewhat diagrammatic longitudinal side view in elevation illustrating a guide roll utilization for metal strip that is being continuously moved in line through an annealing furnace. It also illustrates guide rolls for forward line movement of the strip or workpiece.

FIG. 2 is an enlarged end view in elevation illustrating a roller constructed and employed in accordance with the invention.

And, FIG. 3 is a sectional view on the scale of and taken along the line 3-3 of FIG. 2.

In the drawings, FIG. 1 somewhat diagrammatically illustrates an operation in which a workpiece or metal strip A, such as of steel, is being moved continuously through a heat-treating, annealing or other form of furnace 10 in guided relation on rolls. E and F represent guide rolls of any conventional form which may, if desired, be electric motor driven and which are employed for introducing the strip A into the furnace 10 and for moving it therefrom. The furnace is illustrated as being heated by oil or gas burners 12 and as having a group of guide rolls B, C and D operatively-positioned for rotation therein. Such rolls may be idler or driven rolls as required for the operation. For eliminating the build-up of metal on the roll surfaces, irrespective of whether or not they are fully synchronized with the movement of the workpiece or strip A, I contemplate providing representative rolls, such as B and C, of a construction such as disclosed in FIG. 2. This construction protects opposed guided and roll contacting opposite surfaces of the strip or workpiece length A.

Where, for example, the workpiece length A has only one of its surfaces engaging a guide roll, then it may only be necessary to use one entry (such as B) roll constructed in accordance with the invention, as disclosed in FIGS. 2 and 3. In any event, it has been determined that the use of a somewhat heavy inert gas of the class of nitrogen, argon and neon will, when introduced through openings in a guide roll such as 20, not only act as a protective film between the surfaces of the guide roll and the contact surface of the workpiece, but will also serve as a lubricant therebetween. This eliminates any tendency for a build-up of metal from the strip on the roll surface. It has also been determined that the gas, as thus introduced, tends to follow along or adhere to the applied surface of the workpiece and to thus protect it from the standpoint of a succeeding guide or contact roll that is positioned to engage the same side or surface of the workpiece.

In view of the above, a single gas introducing roll may be sufiicient within a heating furnace, provided that its first roll and subsequent rolls contact the same side of the 3 workpiece A. However, when, as shown in FIG. 1, two sides of the workpiece are contacted by guide rolls, such as B and C, then it has been found advisable to provide both rolls of a gas supply construction in order to protect opposite surfaces, faces or sides of the workpiece or strip A.

Referring particularly to FIGS. 2 and 3, cylindrical contact or guide roll is shown as having a body provided with a hollow interior 20a and a series or group of staggered, radially-outwardly-extending, through gas passageways, ports or holes 20b. As particularly illustrated in FIG. 3, the holes 20b are enlarged or champfered at their outer ends 20c to provide an enlarged area of gas application along the outer, strip-engaging periphery of the cylindrical roll 20. Although the roll 20 may be driven in the customary manner by a motor, such as an electric motor operatively connected to its shaft, for simplicity of illustration, it has been shown as an idler type that is driven by the movement of the strip A. In this connection, the roll 20 has solid end closure or head portions 21 and 23 which respectively carry outwardly-extending end shafts or trunnions 22 and 23. Both the shafts 22 and 24 are shown as extending through side openings in the wall enclosure of the furnace 10, and both are shown as journaled on respective bearing stands 15 and 16, each of which has a bearing assembly 17 that rotatably-carries an associated end shaft.

The stand 15 has an end cap housing 18 for the shaft 22 and the stand 16 has a somewhat similar end cap housing 19 for the shaft 24. The shaft 24, as distinguished from the shaft 22, is shown provided with a central, throughextending passageway or bore 24a that is aligned with a. similar bore 23a in the head 23. A gas supply pipe 26 extends through a hollow bushing 25 that is secured to the cap 19. The pipe 26 is adapted to rotate with the shaft 24 and has its threaded end secured within a female threading in the outer end of the passageway or bore 24:: to thus rotate with the roll 20. Any suitable commercial revolving type of flexible joint G may be used for connecting the rotatable pipe 26 to a stationary gas supply pipe 30. For example, a Barco type 7RSCR joint may be used; this type of joint is distributed by McMasters of Chicago, Ill.

The inert gas is introduced under pressure from any suitable source through control and shut-off valve and supply pipe 34 into a gas heater 31, in order to heat it to a temperature somewhat corresponding to the temperature within the chamber of the furnace 10. As shown in FIG. 2, the gas moves through a closed coil system 33 and is heated by an under-positioned gas or oil burner 32. The heated gas then passes into a header 36 and from the header into individual branch pipe member 30 for a particular roll 20. One or more rolls 20 may be connected in a similar manner to the header 36. The pressure at which the gas is supplied will be preferably at least two pounds over the pressure of the ambient atmosphere within the furnace 10 and up to a maximum of about ten pounds per square inch thereover. As shown, both the furnace 10 and the gas treating guide roller assemblies may both be mounted on a floor or support base 11 in the plant or mill.

The use of a system such as described has the further advantage of permitting the use of a roll surface that is highly polished or finished and which will thus not mar the surface of the workpiece to thus eliminate any tendency for the workpiece to stick thereto. The gas application tends to cool the roll surface or to at least maintain it at a lower temperature than the ambient atmosphere of the furnace to thus further protect it during its operation within the furnace. For example, if the furnace is operating at 1800" F., the gas may be supplied to the associated roll 20 at a slightly lower temperature of, for example, 1700 F. It has been discovered that this does not detract from the actual effectiveness of the temperature required for the annealing or other heat treating operation, but tends to increase the adherence of the inert gas to the surface of the roll as well as the surface of the strip that is moving along the furnace. Although the holes or passageways 20b may have any suitable spacing, I have found that holes 20b of about to A; of an inch in diameter, as surface countersunk at 20c and spaced three to five inches apart, are fully satisfactory in employing the invention.

I claim:

1. In a method of eliminating pick-up and build-up of metal from a continuous workpiece length such as a metal strip on a rotating guide roll employed within a heat treating furnace for guiding the metal strip during heat treatment through the furnace and irrespective of any slippage between the roll and the metal strip, and wherein the roll is rotated at a speed somewhat corresponding to the speed of movement of the strip through the furnace, maintaining the atmosphere of the furnace at a raised heat-treating temperature, continuously moving the metal strip over the surface of the roll through the furnace and heat-treating it with heat supplied by the furnace atmosphere, introducing and continuously supplying an inert gas of the class consisting of nitrogen, argon and neon under positive fluid pressure outwardly from the outer peripheral surface of the roll and as a protective film between opposite surfaces of the roll and the strip, while maintaining the roll surface at a lower temperature than the ambient atmosphere of the furnace, and supplying the inert gas at a raised temperature that is lower than but that approaches the ambient temperature of the furnace atmosphere and at a positive pressure that is at least about two pounds per square inch greater than the atmospheric pressure within the furnace.

2. In a method as defined in claim 1, supplying the inert gas at a temperature of about F. below the operating temperature of the furnace and at a positive pressure within a maximum of about ten pounds per square inch greater than the atmospheric pressure within the furnace.

3. In a method as defined in claim 1, supplying the inert gas as separate streams through staggered holes within the peripheral surface of the roll, and maintaining the streams in a spaced relation of within about three to five inches with respect to each other.

4. In apparatus for guiding a metal strip continuously through a heat treating furnace without metal pick-up and irrespective of slippage of the metal strip with respect to the apparatus, a hollow guide roll operatively positioned within the furnace said guide roll having holes extending in a staggered relation from the hollow interior thereof to the outer peripheral surface thereof and defining a plurality of radially outwardly extending fluid passageways therethrough for continuously supplying heated inert gas to the metal strip being guided thereon during its movement through the furnace, a pair of supporting shafts extending from opposite ends of said roll outwardly through opposite sides of the furnace, a pair of bearing stands adjacent opposite sides of the furnace for rotatably receiving said shafts and mounting said guide roll, one of said shafts having a through-extending hollow passageway therealong for supplying inert gas to the hollow interior of said guide roll, a gas heater connected at an inlet end to a supply pipe for the inert gas, a revolving type of flexible joint connected to the outer end of said hollow shaft, piping from an outlet end of said heater to said joint for supplying heated inert gas through said hollow shaft to said guide roll, means for heating the atmosphere of the furnace to aheat treating temperature, and means for advancing the strip into the furnace over said guide roll and for rotating said roll at approximately the speed of movement of said strip, while supplying the heated inert gas through the peripheral surface of the guide roll and between it and the opposed surface of the metal strip to provide a protective film therebetween and maintain the guide roll at a lower temperature than the ambient heat-treating temperature within the furnace.

5. In an apparatus as defined in claim 4, said holes having a spacing of about 3 to 5 inches with respect to each other about the outer peripheral surface of said guide roll and having enlarged countersunk portions immediately open to said peripheral surface, and said holes having a diameter within a range of about to of an inch.

References Cited UNITED STATES PATENTS 1,948,173 2/1934 Hagan 266-3 5 3,075,679 1/1963 Wadey 22697 X 3,198,499 8/1965 Stanley 22697 X 3,313,462 4/1967 Smith 22697 3,528,493 9/1970 Schultz 2663 US. Cl. X.R. 

